Visible photoenhanced current–voltage characteristics of Au : TiO2 nanocomposite thin films as photoanodes

Abstract

In this investigation, the effect of annealing temperature and concentration of gold nanoparticles on the photoelectrochemical properties of sol–gel deposited Au : TiO2 nanocomposite thin films is studied. Various gold concentrations have been added to the TiO2 thin films and their properties are compared. All the deposited samples are annealed at different temperatures. The optical density spectra of the films show the formation of gold nanoparticles in the films. The optical bandgap energy of the Au : TiO2 films decreases with increasing Au concentration. The crystalline structure of the nanocomposite films is studied by x-ray diffractometry indicating the formation of gold nanocrystals in the anatase TiO2 nanocrystalline thin films. X-ray photoelectron spectroscopy reveals that the presence of gold in the metallic state and the formation of TiO2 are stoichiometric. The photoelectrochemical properties of the Au : TiO2 samples are characterized using a compartment cell containing H2SO4 and KOH as cathodic and anodic electrolytes, respectively. It is found that the addition of Au nanoparticles in TiO2 films enhances the photoresponse of the layer and the addition of gold nanocrystals with an optimum value of 5 mol% resulted in the highest photoelectrochemical activity. Moreover, the photoresponse of the samples is also enhanced with an increase in the annealing temperature.